The current trend in x-ray Computed Tomography (CT) imaging is toward high-speed volume imaging, which requires that a large number of slices of image information be acquired simultaneously. Detector measurement systems (DMS) for these purposes present many challenges, as the number of channels quickly moves from ten thousand to hundreds of thousands and beyond.
The advent of high integration measurement integrated circuits (ICs), which include upwards of 64 to 256 or more channels per chip, allows the design of smaller self-contained modules that can be assembled in yet larger arrays in both the X- and the Z-directions. The challenges presented by such modules include: transferring the regular connections of the photodetector circuit array to the different connections required by the remaining components of the electronic circuitry, protecting nearby electronic components from x-ray damage, preventing the heat generated by the electronic components from affecting the detectors, and so on. Further challenges include building in the requisite mechanical accuracy, and designing a module that can easily be constructed.
CT (Computed Tomography) detectors requiring large slice counts use photodiodes with so-called back-contacts in order to overcome limitations of high density interconnects. For example, the current state-of-the-art CT detectors use a multi-layered ceramic substrate for electrically coupling the photodetectors to corresponding data acquisition electronics. Although the conventional multi-layered ceramic substrate provides interconnectivity as well as provides a change in node density from one side of the ceramic substrate to the other, it is difficult and expensive to manufacture.